Detector for monitoring rotation

ABSTRACT

The present invention relates to a detector  10  for monitoring rotation, in front of which passes a target  19  wherein it is required that the passage frequency thereof be monitored with respect to a normal passage frequency, comprising a sensor unit  11  connected to a microcontroller  20  which delivers a binary output signal  15 . Detector  10  includes means  30  for conversing with the operator, connected to the microcontroller  20  in order to set the detector  10  to a working mode or learning mode, which learning mode enables the microcontroller  20  to measure the normal passage frequency and enables an operator to select an operating range from a plurality of predefined ranges, through the conversational means  30 . The microcontroller  20  calculates from the selected operating range, a triggering frequency and a resetting frequency.

[0001] The present invention concerns a detector for monitoring rotation comprising functions for learning the passage frequency to be monitored, for selecting an operating range and for calculating a triggering frequency, wherein this detector may be used for example, for monitoring underspeed or overspeed of a rotary movement.

[0002] Detectors for monitoring rotation are frequently used in a great number of industries in order to monitor movement, sliding, breakage of a conveyor belt, etc . . . . They have the particularity of combining in a same device, information acquisition functions of a conventional detector by means of a sensor unit and simple processing functions by counting information received by the detector during a given time and by comparing it with a triggering frequency preset on the apparatus, so as to provide a binary signal resulting from this comparison at the output. An economical apparatus is thus obtained, well suited for processing simple underspeed or overspeed problems. However, it is mandatory that the operator may himself adjust the triggering and/or resetting frequency of the device according to the desired application. The adjustment is generally made by using the screw of a potentiometer mounted on the device. This operation is rather tedious if it has to be done accurately because the operator does not have any feedback information on the adjustment which he has just carried out.

[0003] Document FR 2621119 describes a device for signalling the exceeding of a speed limit. This device comprises input means actuated by an operator for storing a reference threshold with which a measured speed will be compared. Document EP 0843177 also describes a device for measuring the speed of a locomotion means wherein an operator may select one or more reference thresholds. However, in addition to the fact that these devices are only provided for monitoring overspeed and not for monitoring subspeed, they do not allow an operator to be able to select different operating ranges about a same reference value, that which involves constraints for an executive in the field of industry.

[0004] The object of the invention is on the one hand to provide an operator with a simplification of the adjustment of the detector, and on the other hand to provide him with greater flexibility in its use by leaving him the possibility of altering the accuracy of the device rapidly, whilst maintaining the most economical solution as possible for such a detector.

[0005] For this purpose, the invention describes a detector for monitoring rotation, in front of which a target passes, wherein it is required that the passage frequency thereof be monitored with respect to a normal passage frequency, comprising a sensor unit sensitive to the passage of the target, connected, through a detection stage, to the input of a microcontroller which delivers a binary output signal by means of a power stage. This detector includes means for conversing with the operator, connected to the microcontroller in order to set the detector in a working mode or in a learning mode, which learning mode enables the microcontroller to measure the normal passage frequency and to select an operating range for the detector.

[0006] The operating range is selected by an operator from a plurality of predefined ranges within the microcontroller through conversational means. The microcontroller calculates, for the normal calculated passage frequency and from the selected operating range, a triggering frequency different from the normal passage frequency and it calculates a resetting frequency between the triggering frequency and the normal passage frequency. For use in subspeed monitoring, the triggering frequency is lower than the normal passage frequency whereas for use in overspeed monitoring, the triggering frequency is greater than the normal passage frequency.

[0007] Other characteristics and advantages will become apparent in the detailed description which follows with reference to an exemplary embodiment and illustrated by the appended drawings wherein:

[0008]FIG. 1 illustrates the simplified internal architecture of a detector with rotation monitoring according to the invention,

[0009]FIG. 2 schematises the response curve of such a detector used in subspeed monitoring,

[0010]FIG. 3 schematises the response curve of such a detector used in overspeed monitoring,

[0011]FIG. 4 schematises the response curve of such a detector used in both subspeed and overspeed monitoring, simultaneously.

[0012] In FIG. 1, a detector 10 is responsible for monitoring the passage frequency of a target 19 in order to detect a subspeed and/or an overspeed relatively to a normal passage frequency. It comprises the following components:

[0013] A sensor unit 11 sensitive to the passage of a target 19 in front of the detector 10, thus forming the information acquisition unit of detector 10; this sensor unit 11 may be a capacitive, magnetic or inductive transducer as shown in FIG. 1, or the receiving unit of a photoelectric or other detector,

[0014] A detection stage 12 connected to sensor unit 11, responsible for amplifying and shaping the signal emitted by the sensor unit towards:

[0015] A microcontroller 20 having an input 21 connected to the output of the detection stage 12 and providing a binary output signal 22,

[0016] A power stage 13 receiving as an input the binary output 22 of the microcontroller, in order to be able to provide the binary output 15 of detector 10, wherein this binary output 15 may be either in the 0 state, or in the 1 state,

[0017] Storage means 23, for example of the EEPROM or FLASH memory type, connected or integrated to the microcontroller 20,

[0018] Operator conversational means 30 connected to the microcontroller 20.

[0019] According to a preferred embodiment, the conversational means 30 only comprise a light emitting diode 31 driven by microcontroller 20 and a push-button 32 in order to retain an economical solution for detector 10.

[0020] Moreover, in order not to increase the electric consumption of the detector 10 as compared with a conventional detector, it is preferable when the microcontroller 20 operates with a very low clock frequency, for example of the order of 32 kHz and a low supply voltage, for example of the order of 3 volts.

[0021] Detector 10 has two operating modes: a working mode and a learning mode. The working mode corresponds to the usual operation of detector 10 wherein it permanently monitors the passage of a target 19 in front of it and provides a binary signal 15 depending on the frequency of passage of this target 19. The learning mode enables the parameterisation of detector 10 to be performed, i.e. it enables the microcontroller 20 to measure a normal passage frequency N, to calculate a triggering frequency D and a resetting frequency R from the measured normal passage frequency N and from a selected operating range.

[0022] When the learning mode is enabled, the operator is informed about this by the light emitting diode 31 and the detector 10 may measure the normal passage frequency N which corresponds to the frequency at which the target 19 should pass in front of the detector 10 during normal operation of the facility. The operator must have the facility operate at a normal rate so that the detector may measure this frequency N. When the microcontroller 20 has performed acquisition of this normal passage frequency N, it reports this to the operator by means of the light emitting diode 31. Thus, in order to simplify his task, no direct adjustment on the detector 10 is required from the operator: he simply has only to put his facility into normal operation so that detector 10 measures the normal passage frequency N.

[0023] In the learning mode, the operator may then himself select an operating range M. This is selected from a plurality of predefined ranges in the memory of microcontroller 20, different from the normal passage frequency N and corresponding to different ranges of use of the detector about a same normal passage frequency N, thus providing great flexibility in the accuracy of the detector 10. According to a preferred embodiment, the operating range is expressed as a percentage of the normal passage frequency N and four predefined ranges may be devised with values equal for example to 5%, 10%, 20%, 30% of the normal passage frequency N. The operator may view the various predefined ranges by scrolling, whereby each range is displayed for example by a different blinking of the light emitting diode 31. He validates the operating range M which he has selected by extended action on the push-button 32.

[0024] According to an equivalent alternate embodiment, the learning mode may be enabled by the operator through his pressing on the push-button 32 for a long time (typically for more than 5 seconds). When the microcontroller 20 has performed acquisition of the normal passage frequency N, it reports this to the operator by means of the light emitting diode 31 and by default it determines the predefined largest operating range M (30% in the example) which thus corresponds to the least constraining use of detector 10, which has the advantage of facilitating the starting of certain applications. To refine the operating range M, the operator must successively press on the push-button 32 (typically for more than two seconds in order to avoid any untimely manoeuvre), in order to select a more accurate operating range M. For example: by pressing on it a first time, the predefined range 20% will be selected and will cause one blink of the light emitting diode 31, then by pressing a second time, the predefined range 10% will be selected and will cause two blinks, finally by pressing a third time the predefined range 5% will be selected and will cause three blinks. When the most accurate predefined operating range M is selected (i.e. 5% in the mentioned example), any further pressing on the push-button 32 will be inoperative except in the case of pressing for a long time which then restarts acquisition of a fresh normal passage frequency N. A flexible and intuitive dialog is thereby obtained with the operator with very economical operator conversational means, which enables him to rapidly refine the accuracy of his detector after having tuned his machine, for example.

[0025] As soon as the operating range M is selected, the microcontroller calculates by itself a triggering frequency D, depending on the operating range M and on the normal passage frequency N. If the detector 10 is used as an underspeed detector, then the triggering frequency D is lower than the normal passage frequency N and is equal to the normal passage frequency N minus the selected operating range M (see the calculation examples hereafter). If the detector 10 is used as an overspeed detector, then the triggering frequency D is larger than the normal passage frequency N and is equal to the normal passage frequency N increased by the operating range M.

[0026] Microcontroller 20 then calculates a resetting frequency R lying between the triggering frequency D and the normal passage frequency N. According to a preferred embodiment, the resetting frequency R lies half-way between the triggering frequency D and the normal passage frequency N. The storage means 23 are used by the microcontroller 20 for notably storing the selected operating range M, the triggering frequency D and the resetting frequency R.

[0027] The operator is not compelled to himself select an operating range M as the microcontroller 20 always has a default value. This default value may either be the largest of the predefined ranges in the microcontroller if this is the first use of detector 10, or the last selected operating range during a previous learning phase of detector 10 and stored in the storage means 23.

[0028] When the normal passage frequency N is measured and the microcontroller 20 has stored the selected operating range M, the triggering frequency D and the resetting frequency R, then the detector 10 resumes the working mode.

[0029] In the working mode, if detector 10 is used as an underspeed detector as shown in FIG. 2, it switches its binary output 15 to a first state (0 or 1, respectively) when the passage frequency for target 19 is lower than the triggering frequency D and it switches its binary output 15 to the second state (1 or 0, respectively) when this passage frequency is greater than the resetting frequency R. If, for example, the operator has selected a operating range M equal to 10%, this means that the detector 10 will switch its binary output 15 to the first state when the passage frequency for target 19 in front of detector 10 is less than the triggering frequency D₁=N−10%*N, i.e.: 0.9*N and the detector 10 will switch its binary output 15 to the second state when the passage frequency for the target 19 in front of detector 10 is greater than the resetting frequency R₁=N−(10/2)%*N, i.e.: 0.95*N.

[0030] If detector 10 is used as an overspeed detector as shown in FIG. 3, it switches its binary output 15 to a first state (0 or 1, respectively) when the passage frequency for target 19 is greater than the triggering frequency D and it switches its binary output 15 to the second state (1 or 0, respectively) when this passage frequency is lower than the resetting frequency R. If, for example, the operator has selected an operating range M equal to 10%, this means that the detector 10 will switch its binary output 15 to the first state when the passage frequency for target 19 in front of detector 10 is larger than the triggering frequency D₂=N+10%*N, i.e.: 1.1*N and detector 10 will switch its binary output 15 to the second state when the passage frequency for the target 19 in front of detector 10 is less than the resetting frequency R₂=N+(10/2)%*N, i.e.: 1.05*N.

[0031] It is possible to contemplate a detector 10 which simultaneously operates both as an underspeed detector and an overspeed detector, as shown in FIG. 4. In this case, from the selected operating range M, the microcontroller 20 uses both triggering frequencies D₁ and D₂, symmetric with respect to the normal frequency N, wherein D₂ is larger than D₁. Operation is as follows: detector 10 switches its binary output 15 to a first state (0 or 1, respectively) when the passage frequency of target 19 is greater than the triggering frequency D₂ or is less the triggering frequency D₁. Detector 10 switches its binary output 15 to the second state (1 or 0, respectively) when the passage frequency of target 19 is less than the resetting frequency R₂ and greater than the resetting frequency R₁.

[0032] Of course, it is possible to devise other detailed alternatives and enhancements and even to contemplate the use of equivalent means without departing from the scope of the invention. 

1. A detector for monitoring rotation, in front of which passes a target (19) wherein it is required that the passage frequency thereof be monitored with respect to a normal passage frequency (N), comprising a sensor unit (11) sensitive to the passage of a target (19), connected, through a detection stage (12), to the input (21) of a microcontroller (20), which provides, by means of a power stage (13), a binary output signal (15) which may take a 0 state or a 1 state, characterized in that the detector (10) includes operator conversational means (30) connected to the microcontroller (20) in order to set the detector (10) in a working mode or in a learning mode, which learning mode enables the microcontroller (20) to measure the normal passage frequency (N) and to select an operating range (M) of detector (10).
 2. The detector for monitoring rotation according to claim 1 , characterized in that the operating range (M) is selected by an operator from a plurality of predefined ranges in the microcontroller (20), through conversational means (30).
 3. The detector for monitoring rotation according to claim 2 , characterized in that the microcontroller (20) calculates, from the normal measured passage frequency (N) and from the selected operating range (M), a triggering frequency (D) different from the normal passage frequency (N).
 4. The detector for monitoring rotation according to claim 3 , characterized in that the microcontroller (20) calculates a resetting frequency (R) lying between the triggering frequency (D) and the normal passage frequency (N).
 5. The detector for monitoring rotation according to claim 4 , characterized in that the resetting frequency (R) lies half-way between the triggering frequency (D) and the normal passage frequency (N).
 6. The detector for monitoring rotation according to claim 4 , characterized in that, for use in monitoring underspeed, the triggering frequency (D) is less than the normal passage frequency (N).
 7. The detector for monitoring rotation according to claim 6 , characterized in that, in the working mode, detector (10) permanently monitors the passage of a target (19), switches its binary output (15) to a first state (0 or 1, respectively) when the passage frequency for the target (19) is less than the triggering frequency (D) and switches its binary output (15) to the second state (1 or 0, respectively) when this passage frequency is greater than the resetting frequency (R).
 8. The detector for monitoring rotation according to claim 4 , characterized in that, for a use in monitoring overspeed, the triggering frequency (D) is greater than the normal passage frequency (N).
 9. The detector for monitoring rotation according to claim 8 , characterized in that, in the working mode, detector (10) permanently monitors the passage of a target (19), switches its binary output (15) to a first state (0 or 1, respectively) when the passage frequency of the target (19) is greater than the triggering frequency (D) and switches its binary output (15) to the second state (1 or 0, respectively) when this passage is less than the resetting frequency (R).
 10. The detector for monitoring rotation according to claim 4 , characterized in that the detector (10) also includes storage means to be used for notably storing the selected operating range (M), the triggering frequency (D) and the resetting frequency (R).
 11. The detector for monitoring rotation according to any of preceding claims, characterized in that the conversational means (30) comprise a push-button (32) and a light emitting diode (31) directly mounted on detector (10). 